Sunday, March 23, 2008

Mars is 'covered in table salt

user posted image rMars appears to be covered in salt crystals from ancient dried-up lakes, new evidence suggests. A Nasa probe has found signs that the southern hemisphere is dusted with chloride mineral, perhaps "table salt". US scientists think the mineral formed when water evaporated from salty lakes or soil billions of years ago. The deposits, similar to salt-pans on Earth, are a good place to search for traces of past life preserved in salt, they report in the journal Science. The evidence comes from a camera on Mars Odyssey, which has been mapping the Red Planet since early 2002. The camera images Mars in the visible and infrared parts of the spectrum in order to work out the distribution of minerals on the surface. It found about 200 places with spectral "fingerprints" consistent with chloride salt deposits. All were in the middle to low latitudes of the ancient, heavily cratered terrain in the southern highlands. Team member Professor Philip Christensen, of the School of Earth and Planetary Exploration at Arizona State University, Tempe, said the most likely chloride mineral "would be good old table salt (sodium chloride)". He said many of the deposits lay in basins with channels leading into them, the kind of feature that is consistent with water flowing in over a long time. He told BBC News: "Two possible mechanisms would be the evaporation of a large body of water (like a salt lake on Earth), or capillary action in the soil that could draw salt-rich water toward the surface, where the water evaporates and the salt is left behind and accumulates.

"Either case is exciting because it implies a large amount of water near the surface." Warmer, wetter: The team - which also includes members from the University of Hawaii, University of Arizona and Stony Brook University - thinks the deposits formed about four billion years ago, when Mars was probably much warmer and wetter.

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